Wood is the medium of construction for innumerable articles used in many facets of contemporary living. For purposes of convenience, health, design, durability, general aesthetics and many others, the wood surface is often treated by one or more finishing operations such as staining, basecoating, glaze coating, topcoating and the like. However, the successful application of these operations depends upon having a proper surface on which to apply the coatings. The natural wood surface is generally too rough and too porous for the optimum performance of the subsequently applied coating. Addressing this problem, those skilled in the art have, in essence, created a composite material which is formed at the wood surface. The composite material consists of a wood cellulose layer on the surface of the article embedded in a nitrocellulose matrix applied to the surface. The composite material is formed by the application of nitrocellulose polymer dissolved in organic diluents to the natural wood surface followed by drying either in air or in an oven. This wood cellulose-nitrocellulose composite that is formed then serves as the surface to be coated. This new surface displays good sandability leaving the sanded surface smooth and essentially non-porous, as is necessary for good performance by the subsequently applied coatings.
However, this method of altering a natural wood to better accept finishing operations has a number of disadvantages which are becoming increasingly important. Because the nitrocellulose polymer must be applied to the natural wood surface dissolved in organic diluents, large amounts of organic solvent are released to the atmosphere upon subsequent drying. This release of organic solvent creates serious problems of hazard due to flammability and explosion potential and problems of health due to exposure of workmen to the solvent vapors in the workplace and exposure of the public when the vapors are vented to the outside atmosphere. Furthermore the loss of the increasingly expensive organic solvent in the drying step has made this method of wood treatment less and less economically attractive. Measures to deal with these problems such as fans and ducting to control or disperse the vapors and recycle operations to salvage the solvent are costly and energy intensive.
Responding to these problems, those skilled in the art have attempted to devise water-borne latex coatings which avoid the use of high levels of organic solvents. Several such systems have been developed but all have proved unsatisfactory for the treatment of natural wood because the sealed wood substrate has heretofore exhibited poor sandability. The dust created by the sanding operation on these treated surfaces rapidly fuses on to the sanding agent (such as sandpaper) and renders the agent useless in a very short time.
A wood cellulose-polymer composite which can be formed as the surface of natural wood by the application of water-borne polymeric material to the natural wood surface and which creates a new surface which has good sandability characteristics in that it can be sanded to a smooth non-porous finish easily without quickly destroying the sanding agent would be of great advantage.